U.S. Pat. No. 3,209,771 teaches the use of gelled bodies for separating two fluids flowing in a pipeline. In U.S. Pat. No. 3,225,787 an attempt is made to improve the technique of U.S. Pat. No. 3,209,771 by employing an elongated gel filled pipeline pig having elastic reinforced rubber sidewalls and thickened ends. The latter technique was employed to overcome the problem of the gelled body of U.S. Pat. No. 3,209,771 breaking down in long pipelines. However, while solving this problem several new problems ensued. First, due to the thick walls of the pig taught in U.S. Pat. No. 3,225,787 the pig lost some of its flexibility and tended to be blocked by "stalactites" located at welded joints in the line. Further, the pig could only be employed in one size pipeline. Canadian Patent No. 903,621 teaches to overcome the blocking problem by employing an elongated gel-filled pipeline pig having thin lateral walls and elastic end walls. The walls are sufficiently thin so that they are ripped by stalactites and flow on without substantial pressure build-up.
An ideal pipeline pig would be a gelled self-sustaining mass which does not break up in line pipelines and which can be readily converted to a liquid for disposal at the end of the flow cycle. Furthermore, it would be preferable if the pig could change size so that it could flow through different size conduits. The present invention concerns a gel-like mass which does not break up in long pipelines and which can readily be returned to a liquid form at the end of the use cycle. In addition the pig can be flowed directly from one size pipe to another. Also, the gelled pig can be employed as a wiper plug to remove various fluids (e.g. hydrocarbons, asphaltines, paraffins), solids and semi-solids such as sand, tar, corrosion products and the like from conduits. The gel of the present invention not only wipes surfaces clean but can absorb a substantial amount of water without breaking down.